Acoustical paint



COATING OR PLASTIC Patented June 30, 1936 I UNITED STATES CrossReference 2,046,296 PATENT OFFICE ACOUSTICAL PAINT No Drawing;

Application May 31, 1930, el'ial No. 458,926

This invention relates to plastic compositions, and has reference moreparticularly to plastic compositions for application to the walls andceilings of buildings for the purpose of correcting the acousticalproperties in said building.

In correcting the acoustical properties of rooms and buildings it iscustomary to apply an acoustical plaster, or other surface, to theceilings or walls of the room, in a comparatively thick layer forabsorbing the sound waves and preventing echoes in the room. Fiberboards and hair felt have been used for this purpose-but they areunsightly in appearance and give little or no decorative effect. After aperiod of time, these acoustical materials become soiled through use andrather unsightly, so that it is desirable to apply a thin layer of anacoustical paint over the acoustical material to give a fresh and cleansurface and improve the appearance of the room. However, it is importantthat this acoustical paint applied to the acoustical plaster does notappreciably reduce the sound absorbing qualities of the acousticalmaterial. It is also sometimes desirable to apply an acoustical paint ina rather thick, sound absorbing layer over a room surface which initself is not sound absorbing, or over an old and soiled coating ofacoustical paint. The decorative effect may also be produced bytexturing our acoustical paint.

An object of this invention, therefore, is to provide a compositionwhich is suitable for application over acoustical plaster, boards, tilesor mats for the purpose of improving the appearance and decorativeeffect of same.

Another object of the invention is to provide an acoustical compositionwhich may be applied to building surfaces, for the purposes of absorbingsound waves; also to improveacoustical surfacing materials in otherrespects hereinafter specified and claimed.

Our improved composition is primarily intended for brush application tothe surfaces of buildings for the purpose of absorbing impinging soundwaves. It preferably contains a substantial amount of fibrous materials,and in order to secure proper brush application, we have found itnecessary to provide special pre-treatment of the fibers in order tosecure a uniform dispersion of same, as well as other qualities. Thispretreatment of the fibrous material consists essentially in coating thefibers with a binder by mixing the fibrous material with the solutioncontaining the binding material, drying, grinding and grading theproduct. While one pretreatment may be suihcient in certain cases, wehave found that two or more pretreatments are desirable, and we shalldesignate these pretreatments as pretreatment M and pretreatment N". Thepretreatments very materially improve the plasticitgifsni brushabilityof our acoustical product.

Pretreatment M ispre ed by adding a mixture of the following:

Parts by weight The wetted mass is placed on screens and dried, thenground through a Prater mill or other pulverizing machine and screenedso that all passes an 8 mesh screen.

Pretreatment N is prepared by adding a mixture of the following:

Parts by weight Mineral wool 45.2 Asbestos No. 7 M 2.6 Pine sawdust(white pine, graded) 4.2

to the following binder solution:

Casein 32.0 Water 141.0 Ca (OH) 2 6 .4 Silicate of soda 22.4

This wetted mass is spread on a screen, dried, ground through aPrater'mill, and then screened so that all passes a 16 mesh screen.

Pretreatment M is a means of incorporating fibrous fillers, which havebeen wetted with an adhesive mixture. This aids in the dispersion of thefillers without greatly decreasing the fiber length of the mineral wooland cottonwood fibers, and without it the material is heavy and dense.The processed wheat or corn paste is a artiall dextrinized starch Cornor other fannaceous astes may be used with varying success.

Eetreatment.N"v contributes greatly to the porosity when used inconjunction with the other ingredients in the formula, and prevents theformation of a skin on the surface of the finished and dried acousticalpaint which would reduce the porosity and sound absorbing qualities. Anexcess of pretreatment N darkens the color of the final composition andincreases the number of surface cracks. It is our belief that 'thesodium lime caseinate precipitated on the surfaces of the fibers by theinteraction of the ingredients in the pretreatment N", swells in the wetmix, and in drying contracts, leaving open and interconnecting poreswhich aid the sound absorbing qualities of the composition. The sodiumsilicate preferred has a NazO:SiOz ratio of 1:531 Having Examiner 11 percent NazO and 31.2 percent 310: and a due to the increase in thepercentage of pumice gravity of 47 B.

This pretreatment of the fibers may be accomplished in a number ofdifferent ways as long as the fibers are coated with the bindingmaterial before mixing with the main part of the composition. and onlythe preferred form of accomplishing these pretreatments is given below.The pretreated fibrous material may also be mixed with the otheringredients in the composition in a number of different ways, and twocharacteristic formulas will be given.

Formula No. 1 consists of the following ingredlents:

' Per cent Iumice (passing 20 mesh, retained on tion.

characteristic in the final composition. The marble gives weight, colorand aids texturing properties besides ma ng a small contribution to theporosity.

The glue gives a stickiness very desirable for brush application. Gluegives a great portion of the final strength and an excess of gluereduces the porosity. Bone glue has given us the best results. The mas apreservative for the wheat paste and affects the viscosity of the glue.The wheat paste modifies the tenacious nature of the glue, increasingthe consistency and contributing to the final strength and hardness. Webelieve furthermore it helps brushing characteristics and plasticity.The gum Karaya greatly increases the consistency and final porosity. Itlightens the wet material and while an excess helps the porosity, itinjures the application. The lithopone helps the color and brushing,giving a plasticity and gel characteristic very desirable for brushapplication. Its use must be controlled since an excess reduces porosityto a marked degree. The tribromophenol acts as a reservative and moldreventative. The oil of sassafras E used to mask the o ec onable phenolodor of the tribromophenol.

In formula No. 2 an increase in the pumice and marble gives betterporosity and lower initial cost, but there is some sacrificing ofdesirable working characteristics and hardness of the final formula.Oxalic acid and paraformaldehyde act as insolubilizing agents on theglue. The paraformaldehyde may 5 added at the job if desired to preventany undesired reactions in the dry mixture. Sodium phosphate increasesthe viscosity of times-a better body to the formula, but is notessential thereto. Other materials have been varied somewhat inproportion,

and marble.

Formula No. 2 is as follows:

Per-cent. Fumice (passing 30 mesh, retained on 48 5 mesh) 16.!

Marble (passing 30 mesh, retained on 48 48 mesh) 13.0 Marble (passing 20mesh, retained on 48 mesh) 28.7 Cold water glue 2.4 Aluminum sulphate(A1:(SO4):.18H2O)..--- 1.3 Wheat past 2.4 Gum Karaya-.. 1.01 Lithopone18.0 Pretreatment "M (Precoated fibrous material) 21.0 Pretreatment N(Precoated fibrous material) 16.0 Tribromophennl 0.2

Oil of sassafras, 4-5 drops per pound of composimesh) 33.4 Cold waterglue 2.0 Aluminum sulphate (Alz(SO4):.18H2O) 1.1 10 Wheat paste 2.0Lithopone m 12.5 Pretreatment "11 (Precoaied fibrous material) 16.7Pretreatment "N" (Precoated fibrous mal5 terial) 13.3 Oxalic acid .1Paraformaldehyde. .2 Karaya gum .83

\Dibasic sodium phosphate 12 20 Various materials may be substituted forthose in our formulas Nos. 1 and 2, with varying success. Instead of thepumice and marble, we may use crushed, other crush pyro hyllite silicaor 25 or graded fiii g fiagria s. Instead of cold water glue, caseinbloo a umen,

or other binding or adhesive material? may He used.

It is thought that carbon dioxide gas is 30 formed by the action of alumon the marble. Potassium orsodi rbona or whiting may e as equivalent gasforming agents to react with the alum. This generated carbon dioxide notonly improves the porosity of the dried paint, but also aids materiallyin preventing the formation of a surface crust which would reduce thesound absorbing efficiency of the paint. Instead of the wheat paste,corn sfg, tapioca or other farinaceous pastes may used. The gum Karayahas the property of forming a thick solution with 50 to 75 parts byweight of water, and when this water dries out, it gives the resultingdried composition a porosity where the space was previously occupied bywater. Gum 45 tra acanth and Irish moss may be substituted for the gumKaraya. ad of the lithopone, other white igments may be used such aszinc oxide, um o e pigments and white lead pigmenmrvatives may e usestead of the tribromopfienol, such as phenol, crew} or beta naEthol,etc. Other aromatic substances mayt use tead oi oil of sassafras, suchas oil 0 cloves, winter reen, ine oil, etc. WoH fibers other thancot'finwoo may be use cm a No. 2 tartaric and citric acid may besubstituted insteme om with varying degrees of success and formaldehyde,lead acetate, or sodium or potass'm de. Instead of the dibasic sodiumphosphate, monosodium ho hate, magesium chloride, soaF'um' Hydroxide orairome alum may be submmmnsimat paste, gum Karaya, tribromophenol, oilof sass'afras, asbestos. cottonwood fibers, sawdust, oxalic acid,paraformaldehyde and sodium phosphate desirable but non-essentialingredients of ourcom- D OIL Our acoustical paint may be colored in anyshade by the addition of a suitable color pigment. The coloring,'texturing and acoustical properties and possibilities, gives to ourpaint a. unique field of usefulness not achieved by other methods ofdecorating. 7

COATING R PLASTIC We would state in conclusion that while theillustrated examples constitute practical embodiments of our invention,we do not wish to limit ourselves precisely to these details, sincemanifestly the same may be considerably varied without departing fromthe spirit of the invention as defined in the appended claims.

Having thus described our invention, we claim as new and desire tosecure by Letters Patent:

1. The step in the preparation of an acoustical composition whichcomprises mixing a fibrous material with a solution containing casein,water, hydrated lime, and silicate of soda, drying said fibrous mass toprecipitate coating material on the surface of said fibers, andpulverizing said fibrous mass.

2. The method of pretreating fibrous material preparatory to mixing withan acoustical composition, which comprises precipitating a coating ofsodium calcium caseinate on the fibers of the fibrous material, dryingthe fibrous material, and pulverizing said fibrous material.

3. A composition oi! matter for acoustical absorption of sound, havingsubstantially the following formula:

Per cent Pumice (passing 20 mesh, retained on 48 mesh) 13.0 Marble(passing 20 mesh, retained on 48 mesh)- 26.65 Cold water (bone) glue 2.4Aluminum sulphate (A12(SO4):.18H2O 1.3 Wheat paste 2.4 Gum Karay 1.05Lithnpnne 16.0 Mixed mineral and vegetable fibers coated with a dextrinbinder 21.0 Mixed mineral and vegetable fibers coated with a caseinbinder 16.0 Tribromophen 0.2

011 of sassafras, 4 to 5 drops per pound of composition. I 4. The methodof preparing an acoustical composition, which comprises mixing a fibrousma terial with a solution containing reactive agents for precipitating awater insoluble caseinate coating material on the surface of saidfibers, drying and puiverizing the wetted fibrous mass to form apretreated fibrous material, and mixing said pretreated fibrous materialwith a granular, inert filler, binding material selected from the groupconsisting of i'arinaceous paste, glue, casein, .and blood albumen, andwith gas forming agents comprising carbonates and acid salts, waterabsorbing gum, a pigment, and a preservative agent.

5. The method of preparing an acoustical composition, which comprisesapplying a water insoluble caseinate coating material to the surface offibers in a fibrous mass containing mixed vegetable and mineral fibers,drying and pulverizing said mass to form a pretreated fibrous material,and mixing said pretreated fibrous material with a granular fillingmaterial, a binding agent selected from the group consisting oiiarinaceous paste, glue, casein and blood albumen, and with gas formingagents, comprising carbonates and acid salts, and a pigment.

6. The step in the method of producing an acoustical composition, whichcomprises mixing Cross Reference 7. An acoustical composition comprising30 to 37% of a mineral and vegetable fibrous material precoated with amixture containing a binding material selected from the group consistingof iarinaceous paste, gum Arabic, casein and sodium silicate solution,39.7 to 50.1% of an inert filler selected from the group consisting ofgranular pumice, marble, burned clay, pyrophyllite, and silica, gasforming agents comprising carbonates and acid salts, a water absorbentgum, and a preservative.

8. An-acoustical paint composition comprising 13.0 to 16.7% of granularpumice, 26.7 to 33.4% of granular marble, 'a binding agent selected fromthe group consisting of farinaceous paste, glue, casein and bloodalbumen, said composition also including gas producing agents comprisingcarbonates and acid salts, a gum having a high water absorbing property,and pigment, and 30 to 37% of a mixed vegetable and mineral fibrousmaterial precoated with a binder selected from the group consisting ofiarinaceous paste, gum Arabic, casein and sodium silicate solution.

9. An acoustical composition comprising 39.7 to 50.1% oil a granularinert material selected from the group consisting of pumice, marble,burned clay, pyrophyliite and silica, and passing a 20 mesh screen andretained on a 48 mesh screen, 30 to 37% of mixed mineral and vegetablefibrous materials precoated with a caseinate binder, a binding agentselected from the group consisting of farinaceous paste,'glue, caseinand blood albumen, and agents comprising carbonates and acid salts forcausing a porous structure in the mass of material for the absorption ofimpinging sound waves.

10. An acoustical composition comprising 30 to 37% of mineral andvegetable fibrous material precoated with a mixture containing anadhesive material selected from the group consisting of Iarinaceouspaste,- Karaya gum, gum Arabic, casein, land sodium silicate; 39.7 to50.1% of an inert filler selected from the group consisting of granularpumice, marble, burned clay, pyrophyilite and silica; glue;insolubilizing agents; gas forming agents comprising carbonates and acidsalts; and a water absorbing gum.

11. An acoustical composition comprising 30 to 37% of mixed mineral andvegetable fibrous material precoated with a mixture containing anadhesive selected from the group consisting of Iarinaceous paste, Karayagum, gum Arabic, casein, and sodium silicate; 39.7 to 50.1% of agranularinert filler material selected from the group consisting of granularpumice, marble, burned clay, pyrophyllite and silica; said mixture alsocontaining glue, wheat paste, a gum having a high water absorbingproperty; gas generating materials comprising carbonates and acid salts,and a preservative.

12. The step in the preparation of an acoustical composition, whichcomprises mixing a fibrous material with a solution of fiber coatingadhesive materials selected from the group consisting of iarinaceouspaste, Karaya gum, gum Arabic. casein and sodium silicate; and dryingand pulverizing the wetted mass to form a pretreated material suitablefor use in an acoustical coating composition.

CARLISLE K. ROOS.

JAMES S. OFFU'IT.

HERMAN A. SCHOLZ.

EXcimi ner-

